Computer systems may include different resources used by one or more host processors. Resources and host processors in a computer system may be interconnected by one or more communication connections. These resources may include, for example, data storage systems, such as the Symmetrix™ or Clariion™ family of data storage systems manufactured by EMC Corporation. These data storage systems may be coupled to one or more host processors and provide storage services to each host processor. An example data storage system may include one or more data storage devices, such as those of the Symmetrix™ family, that are connected together and may be used to provide common data storage for one or more host processors in a computer system.
A host processor may perform a variety of data processing tasks and operations using the data storage system. For example, a host processor may perform basic system I/O operations in connection with data requests such as data read and write operations. Host processor systems may store and retrieve data using a storage device containing a plurality of host interface units, disk drives, and disk interface units. Such storage devices are provided, for example, by EMC Corporation of Hopkinton, Mass. and disclosed in U.S. Pat. No. 5,206,939 to Yanai et al., U.S. Pat. No. 5,778,394 to Galtzur et al., U.S. Pat. No. 5,845,147 to Vishlitzky et al., and U.S. Pat. No. 5,857,208 to Ofek. The host systems access the storage device through a plurality of channels provided therewith. Host systems provide data and access control information through the channels to the storage device and storage device provides data to the host systems also through the channels. The host systems do not address the disk drives of the storage device directly, but rather, access what appears to the host systems as a plurality of logical disk units. The logical disk units either may or may not correspond to the actual disk drives. Allowing multiple host systems to access the single storage device unit allows the host systems to share data stored therein.
It is desirable to copy or replicate data for a variety of different reasons, such as, for example, database-related data may be critical to a business so it is important to make sure is not lost due to problems with the computer systems, such as for example, loss of electrical power. However, there are costs associated with backing up or otherwise copying or replicating data. Such costs include the data being unavailable to an application that may require access to it. For example, in a normal business operation, not as a production environment, data may be needed for an update or in relation to a transaction on a close to full-time (i.e. 24 hours a day, 7 days a week) basis.
To provide for data security, replicas or copies of production data are often transferred out of the production environment into a replica environment including a replica storage system. Unfortunately, if a problem occurs with the production environment there may be an inconsistency between data volumes stored on the production environment's data storage system and supposedly replica data volumes copied to the replica environment. There is a need for some low-cost way to reduce such inconsistencies that is simple to use in a data storage environment.